In 2009, an unidentified disease was observed on commercial
tomatillo (Physalis philadelphica Lam.) grown in greenhouses in central
coastal California (San Benito Co.). Disease incidence was well over 50%;
disease severity could be high, with some plants having all foliage, except for
the youngest new leaves, turning yellow and withering. Affected leaves developed
adaxial spots that first were light green, later turned bright yellow, and
eventually became necrotic. Spots were generally round, sometimes vein-delimited
when occurring near major leaf veins, and 0.5-1.0 cm in diameter (Fig. 1).
Corresponding abaxial sides of spots were white with conidiophores emerging from
stomata in fascicles (Fig. 2). Mature conidia were not seen. Disease was most
severe on older leaves, where spots coalesced and resulted in senescence and
drying of entire leaves. Sori contained teliospores that were subspheroidal to
angular, transparent to pale green, and (9-)9.5-15.5(-15.5) µm in diameter (Fig.
3). Teliospore walls were smooth, consisted of one or two layers, and were
(0.5-)1-2.5 µm thick (Fig. 4).

Approximately 1 mm³ of sorus material was excised, DNA
extracted, and the ITS region amplified using protocols described previously (4)
except that primer P3 (5) was substituted for ITS4. The resulting amplicon was
619 bp. Compared to a Genbank ITS sequence for Entyloma australe (gi
27371349), sequences differed by one base substitution and one indel (>99%
similarity). Additional Entyloma species reported on other genera in the
Solanaceae include E. petuniae Speg., E. nierenbergiae Lagerh.,
and E. browalliae Syd. (2). Of these, only E. browalliae is
represented in GenBank, by ITS sequences (gi 61387339 and gi 27371351). The 588
bp region common to both of those sequences is identical. Comparison of those
sequences with the sequence we generated revealed that the E. browalliae
sequences differed from the E. australe sequences in 2-3 indels and 4-5
base changes and were consistent with a phylogenetic study that maintained E.
australe and E. browalliae as distinct species (1). The ITS sequence
was deposited with GenBank and a voucher specimen deposited with the Mycology
Herbarium of the Plant Pathology Department at Washington State University.

Pathogenicity was confirmed by inoculating plants with inoculum
prepared by grinding diseased leaves, straining out leaf material, and spraying
the resulting teliospore suspension (1 × 104 spores/ml) onto healthy
tomatillo plants. Plants were incubated in a humidity chamber for 24 hours and
then kept in a greenhouse. After 14 days, leaf smut disease developed on
inoculated plants and the same pathogen was observed in diseased tissue; plants
treated with water did not develop the disease.

The causal agent was identified as Entyloma australe Speg.
based on host and on pathogen morphology and ITS region sequence. The size,
shape, and color of teliospores and the production of fascicles of conidiophores
fit the descriptions for E. australe (3). This appears to be the
only Entyloma species occurring on Physalis (2,3). Fischer (3)
included 15 named species of Physalis in the host range for E.
australe, as well as species of solanaceous genera Lycopersicon, Quincula,
and Solanum. This report appears to be the first record of E. australe
on P. philadelphica.

4. Glawe, D. A., Dugan, F. M., Liu, Y., and Rogers, J. D. 2005. First record and characterization of a powdery mildew (Erysiphales) on a member of the Juncaginaceae: Leveillula taurica on Triglochin maritima. Mycol. Progress 4:291-298.